Method of manufacturing cellulose



Oct; 31 1939. I E. WAENERLUND Re. 21,251

METHOD OF MANUFACTURING CELLULOSE ACCORDING TO THE SULPHITE METHOD Original Filed Sent. 8, 1930 J. E. Wzenar/un/ INVeN'm I Wald Reisaued Oct. 31, I939 Re,

METHOD .OF MANUFACTURING CELLULOSE ACCORDING TO THE SULPHITE METHOD Torsten E. Waenerlund, Domsjo, Ornskoldsvik, Sweden, assignor to M och Domsjii Aktiebolag, Ornskoldsvik, Sweden Original No. 1,809,499, dated June 9, 1931, Serial No. 480,530, September 8, 1930. Application for reissue April 4, 1939, Serial No. 266,031. In Sweden February 20, 1929 4 Claims. (Cl. 92-11 featuring a sulph liqu r (c oking acid) with a finished cooking. These gases and liquids give ry hi h per enta e of S0:- Th ar ri off one part of their heat to the-cooking acid In feature of the invention consists in this that the order to obtain a, higher temperature difference in raw sulphite liquor 0 Which a known the preheater between the heating medium and contains calcium bisulphitc a d ee 02 as it the cooking acid the currents of lye and gases are comes from the acid towers and before being inregulated by means of the valve 23 in the con- 10 trod-Heed into the digestcr is au d t D thrcllgh duit 52 between the preheater and the absorption an absorption tower where it is enriched with $02 tower 4, the valves 53-54 located before the pre-v ccming P tly from the waste gases esc p n fro heater being then fully opened. By this means h boiler d P y from heated acid, wherethe heat'delivering medium will have the same te the aw acid, after having been enriched temperature as the content of the digester when 15 with S0: in this manner, is caused to pass through it passes through the preheater. n a Drchca-tcr being e ed by eans O Waste From the preheater 5 cooled lye and waste as s and Wa e lye from the digester. The raw gases are led through the conduit 52 to the lower acid having been treated in such a. manner is part of the absorption tower 4, whereafter in this then t ed into a storage pta le f m tower the s02 gas is absorbed by the raw acid which the same, after having been further heatcirculating through said tower. The upper part if c y, ay b di ectly carried over to the of the absorption tower is through the conduit 4|! digester, or'even it is first introduced into a secconnected with the acid tower, so that S02 gases d p c e Which s ntained filled with which may not have been absorbed in the absorpa the a d in d c P c ng held in tion tower are recovered and utilized in the acid 25 continuous circulation through a preheater, so tower. that it is heated tothe required temperature suit- Those parts of the waste lye and of th ably 100-120" C., before being introduced into the densate from the gases, which are not to be mixed d csterwith the raw acid are removed from the conduit A form of embodiment of the method is d8- 52 through the valve 24' and conduit 55. '30 scribed. in the following specification, reference The acid which has been enriched with free. being h d to the acc panyin drawing, where S02 in the absorption tower 4 is pumped in the an pp tus system for the execution of the previously indicated manner through the premethod is schematically shown. This apparatus heate'r5 to the receptacle 12 into which it enters system also forms part of the invention. preheated to a temperature of about -60 C.

The present invention refers to a method of cooking sulphite-cellulose which has for its ob- J'ect to utilize the heat of the waste gases and the vwaste lye from the digester or boiler for manu- Through theconduit 58 raw acid 'is supplied from the acid towers (not shown) to the receptacle 2 from which said acid is through the conduit 3 pumped over to the top of the absorption tower 4 which for efl'ecting a good absorption is filled with acid-proof material, for instance so-called spiral bodies. To the lower end of the absorption tower are connected two pumps 1 and 8, one 1 of which causes a quantity of acid controlled by the valve 20 to circulate either through the whole tower or through a certain part of the lower end of the same, which may be regulated by the valves 2| and 22. The other pump 8 has its suction tube situated on a higher level than the suction tube of the pump 1 and forces the acid through the preheater 5 and from there through the conduit 5a'to the receptacle 12. The preheater 5 is provided with a heating element consisting of tubes, Through the same is forced through the conduits 50 and 5| as a heating medium partly lye taken from the digester may be introduced into'the acid out from the digester during the cooking opera-- tion, partly gases escaping from the digester during the cooking operation and partly hot waste lye which is taken out from the digester after In order to avoid the formation of a vacuum and of too-high a pressure at varying liquid levels in k the receptacle 12 the gas chamber of the latter is by means of an automatically acting valve 28 and the conduit 42 connected with the gas chamber a of the absorption tower, so that the acid receptacle 12 is through the absorption tower put into connection with the gas conduit 40 of the. acid tower. Through the conduit 51 the waste gases in the lower part of the receptacle 12. n

From thereceptacle 12 the acid may be carried over to the receptacle 13 which latter is continuously filled with cooking acid heated to about -120" C. The carrying over of the acid from receptacle 12 to receptacle 13 is executed in connection with the fillingof the digester with acid. Then the valves 25. 26 and 21 are opened so that the acid is forced by means of the pump 9 from the receptacle 12 to the bottom of the receptacle i l3, where it forces out hot acid from the latter, which hot acid through the valve 21 and the conduit 4| is brought over from the top of the receptacle l3 and into the digester. The pumping continues until the digester is filled with acid, whereafter the pump is stopped and the last mentioned valves are closed. The receptacle Ills then still filled with acid which is colder in the lower part of the same than in the upper part.

The heating of the cooking acid in the receptacle 13 takes place indirectly by means of steam from the'conduit 5G in the preheater 6 through which acid is held in circulation through the conduit 43 and the pump Ill. A dangerous pressure which may be created during the heating operation is balanced by means of any suitable arrangement, for instance a conduit 44 between the bottoms of both the receptacles and a valve 39 in said conduit.

It is evident that several variations of the process are possible without departing from the scope of the invention. Thus for instance it will be possible to use instead of the absorption tower 4 several such towers of inferior height each such tower of low height working in the same manner as above describedin connectionwith the absorption tower 4. Moreover, it is not necessary to use the receptacle 13 in which case only the receptacle [2 is used and is then connected with the preheater 6 in the same manner as shown ;in the drawing in connection with the receptacle 13 so that the acid will be sufliciently heated before being introduced into the digester. However, from several points of view it may be advantageous to 'use two receptacles I2 and 13, as the counter pressures will be more favourable and, moreover, a purer acid may be taken out from the receptacle 13 if the latter cooperates with the receptacle 12 than would be the case if acid was taken out directly from the latter. If necessary the acid may be further heated between the receptacles l2 and I3.

Besides the advantages in respect of heat econ omy and with regard to the possibility of obtaining an acid containing a high percentage (8% or more) of free S02 the invention offers the following advantages:

The removing of the gases from the digester may take place in a more quick and complete manner due to the fact that the counter pressure may be regulated as far as down to the atmospheric pressure. Previously the waste gases have as a rule after cooling been introduced directly into the acid receptacles in which case partly the absorption has been very bad and partly the removing of the gases from the boiler has been very slow due to an increasing counterpressure.

Due to the fact that the finished cooking acid is taken out from the top of the receptacle 13 the same may be freed fromsludge and other impurities being injurious for the cooking operation. This is rendered possible in such a manner that the circulation pump I0 is stopped some I claim: 1. Method of manufacturing cellulose by cooking cellulosic material in a digester with a cooking acid of high\percentage of free S02, comprising causing the cold raw acid, before .introducing the same into the digester, to pass through an absorption apparatus, enriching the same in said apparatus withSOz at atmospheric pressure, passing the acid thus enriched through a 'heat transmission apparatus, introducing into said apparatus as heating medium warm waste products from the digester and leading said heating medium, after it has given off heat to the acid, into the absorption apparatus, forcing the acid thus enriched and heated into a storage \receptacle, heating the same and introducing it into the digester for cooking cellulosic material therewith under pressure.

2. Method of manufacturing cellulose by cooking cellulosic material in a digester with a cooking acid of high percentage of free S02, comprising causing the cold raw acid, before introducing the same into the digester, to pass through an absorption apparatus, circulating said acid through said apparatus so as to enrich the same with S02 at atmospheric pressure, forcing the acid thus enriched through a heat transmission apparatus, leading through said apparatus as heating medium hot' waste gases and waste lye from the digester and introducing such gases and lye, after having given off heat to the acid, into the absorption apparatus, forcing the acid thus enriched and heated into the lower part of a storage receptacle, forcing such acid therefrom into the lower part of another storage receptacle, circulating the acid in said receptacle through a heating element, leading off acid from the top portion of said receptacle and into the digester, and cooking cellulosic material therewith in said digester.

3. Apparatus system for making acid sulphite liquor with high percentage of free S02, comprising in combination an absorption apparatus,

,a heat transmitting apparatus and a storage tank, means for introducing raw acid from the acid tower into said absorption apparatus, means for circulating the acid within said apparatus, means for leading through said heat transmitting apparatus waste gases and lye from the digester and means for introducing the same into the absorption apparatus, means for forcing the enriched and heated acid from .the absorption apparatus through the heat exchange apparatus and therefrdm to a storage tank, and means for further heating the acid and for forcing it into the digester. v

4. In an apparatus system according to claim 3, the combination with the receptacle receiving heated and enriched acid from the heat exchange apparatus of a second receptaizle for acid, means for carrying over acid from said first receptacle to the second receptacle, means for circulating the acid in the second receptacle through a heating element, and means for forcing the acid from the top of the second receptacle into the boiler.

TQRSTEN E. WAENERLUND. 

